This technology relates to reconfigurable flexible actuators with hard components. In particular, this invention relates to the combination of soft robotic manipulators with hard modular components.
An example of a “robot” is an automatically controlled, programmable, multipurpose manipulator. A robot can perform its function at a fixed location, or in motion. Robotics is a field of enormous (and growing) importance, in fields from assembly to surgery.
Most robotic systems are “hard”, that is, composed of metallic structures with joints based on conventional bearings. These structures are often modeled after animal limbs (although structures not found in nature—for example, wheels and treads—are also common in mobile robots).
Soft robotic actuators find inspiration in nature. For example, animals without skeletons (such as squid and starfish) present new opportunities in robotic structures, and offer solutions to problems such as the gripping of soft or fragile objects that are challenging to address with hard robots. The mechanisms of actuation and locomotion used by squid and other invertebrates often rely on elastomeric (e.g. “soft”) structures and on actuation elements (e.g. hydrostats) that are uncommon in vertebrates. Soft actuators use pneumatic or hydraulic systems for movement, provide biomimetic and non-biomimetic structures for actuation, gripping, sensing, locomotion, and other functions.
Over the last several years, soft robotic manipulators have generated significant interest due to their wide range of potential applications that are challenging for “hard” robots. For example, soft robots can handle delicate objects such as eggs because the surface of soft robots can conform to the shape of the handled objects. Soft robots can also fit into places that are challenging for hard robots. For instance, a soft robot can fit under a door jam by deflating itself. In addition, soft robots can move in an environment that are challenging for hard robots. For instance, soft robots can maneuver on non-stiff surfaces, such as mud, clay, gels, or in fluids such as water.
Soft robots such as grippers and tentacles can execute highly sophisticated motions without elaborate sensor-feedback system. Complex motions exhibited by soft robots can be initiated by a single pneumatic input and can be pre-programmed by the combination of elastomers and the geometry of the pneumatic networks present in these elastomeric devices. These robots are inexpensive to fabricate by soft lithography and are well suited for handling fragile objects (e.g., uncooked eggs).
Soft lithography can be used to fabricate the soft robots because this technique enables rapid prototyping and replication of internal pneumatic networks. Although these soft robots (e.g., grippers, walkers, and tentacles) with planar or simple body plans can be rapidly fabricated from silicone elastomers using soft lithography, these robots are not easily reconfigurable.
In addition, expanding the capability of soft robots for the fabrication of advanced robotic systems demands integration of composite materials (e.g., thermoplastics, metals) or implementation of complex three-dimensional pneumatic networks that are difficult to mold directly in a single step using soft lithography alone. Many characteristics (e.g., high rigidity, high thermal conductivity, and strong resistance against abrasion) of hard materials are difficult, if not impossible, to replicate using soft or flexible materials. Methods such as computer-numeric-control milling (CNC) or injection-molding can be used for the fabrication of modules made of metal or rigid plastics. 3D printing is advantageous for prototyping hard thermoplastics because it enables rapid fabrication of units that have complicated internal network of three-dimensional channels.
Various methods (e.g., chemical, mechanical, magnetic) exist for connecting modules made of similar or different materials into robots. Chemical glue or adhesives can be applied to the interface between two modules for bonding; however, the structures assembled by permanent adhesives cannot be readily disassembled without damaging the original units. Reversible adhesives have their own limitations and often require heating to sever the bond. Mechanical connectors such as bolts or knuckle joints in hard robotics are both sturdy and reversible, however, these connections require precise alignment for docking of the matching pieces, and thus necessitate the use of sophisticated system of sensor, feedback, and control for remote or automated assembly and disassembly.